Metagenomic and proteomic analyses reveal similar reproductive microbial profiles and shared functional pathways in uterine immune regulation in mares and jennies.
Authors: da Silva-Álvarez Eva, Gómez-Arrones Vanessa, Correa-Fiz Florencia, Martín-Cano Francisco Eduardo, Gaitskell-Phillips Gemma, Carrasco Juan Jesús, Rey Joaquín, Aparicio Inés María, Peña Fernando Juan, Alonso Juan Manuel, Ortega-Ferrusola Cristina
Journal: PloS one
Summary
# Editorial Summary Researchers employed 16S rRNA gene sequencing and liquid chromatography-tandem mass spectrometry to characterise the vaginal and uterine microbiota alongside immune protein expression in 18 healthy mares and 14 jennies, seeking to identify interspecies differences in reproductive microbial communities and their role in uterine immune homeostasis. Whilst the overall taxonomic composition proved remarkably similar between species, β-diversity clustering revealed distinct separation, with only two vaginal and five uterine bacterial taxa significantly differing; notably, Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria dominated both species' uteri, including genera commonly implicated in endometritis such as Streptococcus, Pseudomonas and Staphylococcus, whilst protective Lactobacillus was largely absent. Functional pathway prediction (PICRUSt and KEGG analysis) indicated minimal variation in metabolic capabilities between species despite compositional differences, with proteomic analysis revealing substantial upregulation of proteins associated with adaptive immunity, innate defence mechanisms and TGF-β receptor signalling in both mares and jennies. The findings suggest the uterine microbiota actively participates in immune regulation through specific metabolic pathways, implying that microbial dysbiosis linked to pathogenic genera might compromise immune balance rather than simply representing secondary colonisation during disease. Clinically, these results support further investigation into whether targeted manipulation of the uterine microbiota—through probiotic or prebiotic strategies—could enhance reproductive health and reduce endometritis incidence, particularly given the notable absence of beneficial Lactobacillus in both equine species.
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Practical Takeaways
- •The natural equine uterine microbiota includes bacteria commonly associated with endometritis; distinguishing pathogenic overgrowth from normal colonization requires further clinical research rather than microbial identification alone.
- •Absence of protective Lactobacillus in mares and jennies may explain differences in reproductive tract immunity compared to other species—probiotic strategies based on other mammals may not be directly applicable.
- •Uterine immune function appears intimately linked to resident microbiota composition; management strategies should consider preserving beneficial microbial-immune interactions rather than pursuing microbiota elimination.
Key Findings
- •Uterine microbiota of both mares and jennies dominated by Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria with taxa commonly associated with endometritis including Streptococcus, Pseudomonas, Bacillus, Corynebacterium, and Staphylococcus.
- •Lactobacillus was minimal or absent in equine reproductive tracts despite its protective role in other mammalian reproductive systems.
- •Proteomic analysis identified overexpressed uterine proteins in both species linked to adaptive and innate immune regulation, suggesting active microbial-host immunomodulatory interactions.
- •Predicted functional pathways via PICRUSt showed minimal variation between species despite compositional microbiota differences, indicating conserved metabolic mechanisms for immune balance.